Profile dressing device for grinding wheels



Feb. 18, 1964 R. E. PRICE ETAL 3,121,423

PROFILE DRESSING DEVICE FOR GRINDING WHEELS Filed June 3. 1,960 5 Sheets-S Willi/i INVENTORS RALPH 5- PRICE ORNE Feb. 18, 1964 R. E. PRICE ETAL 3,121,423

PROFILE DRESSING DEVICE FOR GRINDING WHEELS Filed June 3. 1960 5 Sheets-Sheet 2 I I l I INVENTOR l EAL PH E. PRICE 8 BY HAROLD E-BALS/GEI? ATTORNEY Feb. 18, 1964 R. E, PRICE ETAL PROFILE DRESSING DEVICE FOR GRINDING WHEELS 5 Sheets-Sheet 3 Filed June 3. 1960 INVENTOR RALPH E.PR/CE BY HAROLD E-BALS/GER 1 M ORNEY Feb. 18, 1964 R. E. PRICE ETAL 3,

PROFILE DRESSING DEVICE FOR GRINDING WHEELS Filed June 5. 1960 5 Sheets-$heet 4 DEE-SSE? IOC P INVENTOR RALPH E. PRICE BY HAROLD E..BALS/GER ATTORNEY Feb. 18, 1964 R. E. PRICE ETAL PROFILE DRESSING DEVICE FOR GRINDING WHEELS Filed June 5. 1960 5 Sheets-Sheet 5 INVENTOR RALPH E. PRICE BY HAROLD EBAL'SIGER United States Patent 3,121,423 PROFILE DRESSENG DEVICE FOR GRINDING WHEELS Ralph E. Price and Harold E. Balsiger, Waynesboro, Pa., assignors to Landis Tool Company, Waynesboro, Pa. Filed June 3, 1960, Ser. No. 33,673 18 Claims. (Cl. 125-11) This invention relates to apparatus for dressing grinding wheels, particularly grinding wheels having a cylindrical face and rounded corners.

A common use for such grinding wheels is the grinding of crankpins of automotive crankshafts.

In the grinding of crankpins, three surfaces of the crankpin are involved, the side walls, the corners or edges, and the body of the pin. The comers must be formed to a smooth curve joining the body of the pin and the side walls.

In order to form the curved portions of a crankpin, they must first be formed on the grinding wheel. One of the biggest problems in forming such corners on grinding wheels is that of providing a smooth blend of the curved portions with the straight portions of the grinding wheels. This includes the sides of the wheel as well as the face. Another problem is to provide an acceptable curvature of each corner and to maintain uniformity of said curvature.

Many attempts have been made to provide such a dressing device, but even today, the common practice in dressing corners on such grinding wvheels is to apply a piece of abrasive material manually. Most of the mechanical devices for performing this dressing operation make use of single point diamond tools. However, the rate of diamond wear is such that first, there is a continuous problem of maintaining the face of the grinding wheel straight because diamond wear often results in a tapered face. Secondly, on the corners of the grinding wheel, diamond wear causes the diamond to follow a path ditTeren-t from the forming bar or whatever means is used to guide the diamond around the corners.

It is desirable that the entire 90 of the corners be dressed by the dressing tool. One type of dressing tool for this purpose causes the entire diamond to swing about the corners so that the same surface of the diamond is applied to the curved portion of the wheel as to the face. This requires an elaborate mechanism to assure a smooth blending and to reduce the rate of diamond wear, usually by automatically turning the diamond after each dressing operation.

The simplest form of dressing device for a contour grinding wheel is one which uses a profile bar and follower to guide the dressing tool. The principal disadvantage of this type of dresser guiding device is the limitation so far as the angle of inclination along which the follower will move in response to the traverse movement. Under most favorable conditions, the maximum angle is approximately 60. This difliculty occurs when the follower is being guided in a direction to move the dresser radially away from the wheel axis. There is no such problem when the dresser and follower are moving toward the wheel axis because movement in this direction is usually assisted by gravity or some other means for maintaining contact between the follower and profile bar.

However, another problem is presented due to the fact that the straight line traverse movement required to dress the first half of the corner, particularly with a roller-type dresser, is substantially greater than the straight line traverse movement required to dress the second half of the corner. In both cases, the straight line traverse movement is much greater than the length of the surface of the corner. With a uniform traverse speed, which is conventional practice, the second half of the corner would be 3,121,423 Patented Feb. 18, 1964 dressed much more rapidly than the first half. The result of such dressing is a poor quality of finish on the workpiece on that portion of the corner adjacent to the side wall of a crankpin.

Furthermore, the time required to dress the first half of the corner is substantially greater than the time required to dress a corresponding piston on the face of the wheel. This is because of the fact that the traverse movement for dressing a portion of the radius for this type dresser is much greater than the actual length of wheel surface acted on by the dressing tool. For example, at normal dressing speed, it may take five seconds to traverse the dressing tool across the first half of the corner of the wheel, whereas, a similar distance on the face of the wheel would require only one second. Therefore, in order to get the same dressing action on the first half of the wheel corner, the speed of the traverse movement could be increased to dress the first half of the corner in one second, thus saving four seconds for each corner or eight seconds in a total dressing time of approximately fifty seconds, a saving of 15%.

While the most important application for this invention, at present, is the dressing of a Wheel having surfaces parallel to and perpendicular to the axis of the grinding wheel and rounded corners joining said surfaces, as illustrated, it may be used with any type of guiding means for any shape of wheel for which it is desirable to change the rate of the traverse movement of the dresser during certain parts of the dressing operation.

It is, therefore, an object of the present invention to provide means for dressing a grinding wheel having surfaces perpendicular to the axis of the wheel as well as surfaces parallel with said axis.

Another object is to provide a smooth curve on the corner of a grinding wheel.

Another object is to provide means for starting the dressing operation with the dressing tool engaging the grinding wheel at a point on the curve where the inclination is such that it can be traversed by the follower on the forming bar.

Another object is to provide means for maintaining contact between the follower and forming bar.

Another object is to provide means for overcoming said contact maintaining means in order to move said dressing tool and follower to the radial position from which the dressing operation begins.

Another object is to discontinue the operation of said contact maintaining means at an intermediate point in the movement of the dresser across the face of the grindin g wheel.

Another object is to utilize the radial component of the contact maintaining means to assist in guiding the dresser along the curved portion of the grinding wheel toward the wheel axis, that is, in a direction transverse to the direction of traverse.

Another object is to use a power-operated diamond wheel rotatable about an axis normal to the grinding wheel axis and rotatable in a plane other than a radial plane through the grinding wheel axis.

Another object is to arrange the dressing roller either by tilting or by changing its elevation relative to the grinding wheel so that only a portion of the width of said roller face engages the grinding wheel to prolong the period during which at least part of the operative face of the dressing roller retains its original diameter which is the same as that of the follower and thus requires no adjustment to maintain uniformity of contour on the curved portion of the grinding wheel contour.

Another object is to provide control means for the traverse movement to advance the dressing tool into operative relation with the grinding wheel to pass the dresser across the grinding wheel at a suitable dressing speed and to maintain this dressing speed between the dressing tool and the wheel as the dressing tool moves around the corner of the wheel by increasing or decreasing the rate of the traverse movement.

Another object is to provide control means for the traverse motor which will make appropriate changes in the speed of said motor to maintain a constant speed relation between the dressing tool and the wheel during movement of the dressing tool around the corner.

FIG. 1 is a partial end elevation of a grinding machine showing the mounting of the dressing device.

'FIG. 2 is a partial rear elevation showing the limit switc'hesactuated by the traverse movement.

7 FIG. 3 is a partial plan view showing-the limit switches actuated by the in and-out movement of the dresser.

FIG. 4 is a schematic plan view of a dressing device using a-rotatable diamond roller.

FIG. 5 is similar to FIG. 4 except that the dressing device is a pair of single point diamonds.

FIG. -6:is a diagram superimposed on a section of a grinding wheel to identify certain points in the dressing c cle.

FIG. -'7 is a partial end elevation showing the angular relation between the dressing roller and the grinding wheel.

FIG. 8 is a partial right hand view Showing the lift and hold-down cylinders.

[FIG 9 is a'hydraulicand electric circuit.

FIG. 10 is sketch showing the ratio between straight line traverse movements ,for different portions of the dresser travel around'the corner of a grinding wheel when using a roller-type dresser guided by a profile bar.

FIG. 11 is a variation of a portion of FIG. 9 showing an alternate arrangement for providing the fast, normal, and slow traverse speeds for the dresser traverse movement.

FIG. 12 is a portion of FIG. :1 enlarged, showing the angular relation between the dressing roller and the grinding wheel.

'Base member 10 is .mounted on .the wheelbase of a grinding machine (not shown). The top portion of base member 10 has a carriage 1 1 slidably mounted thereon for movement in a direction parallel to the axis of wheel 15. Dresser slide 12 'is slidably mounted on carriage 11 for movement transversely of carriage 11 toward and from grinding wheel 15.

Dresser bar 25 is mounted in slide 12 for adjustment relative to slide 12 to feed or adjust a dressing tool radially toward and from wheel 15. Such adjustment may be effected manually by hand wheel 26 operable through suitable gearing and an adjusting screw (not shown) or automatically by well-known means also not shown.

The dressing tool consists of a diamond roller 30 rotatable in 'a plane perpendicular to the plane of grinding wheel 15. Roller 30 is driven by motor 31. Motor 31 and roller 30 are mounted on support member 32 which, in turn is mounted for endwise adjustment on member 33. Member 33 is attached to bar 25 and arranged for angular adjustment about the axis of bar '25. A graduated ring 34 serves to indicate the extent of adjustment.

The angular relation between the face of roller 30 and that of grinding Wheel as shown-in FIG. 1, is such that the lower corner of roller 30' engages grinding wheel 15. This 'maylbe accomplished as shown in FIG. 12 by tilting the axis of said roller relative to the radial path of adjustment of dresser bar -25. A similar angular relation may be accomplished without tilting the roller by elevating said roller 30 to a point where its plane of rotation does notinclude the center of grinding wheel '15. However, this latter arrangement does not permit the adjustment of roller 36) radially of the grinding wheel which would be a disadvantage because the dressing operation is performed automatically and includes compensation for wear and dressing which must be performed on a radial path. As roller wears, the contact between grinding Wheel 15 and roller 30 is gradually extended across the entire face of roller 30. This angular relation is shown also schematically in FIG. 7.

So long as part of the dressing roller retains its original diameter, the shape of the grinding wheel will not be affected by wear on the roller. As the maximum diameter of the dressing roller is lost due to wear, the roller will no longer follow the proper path along the corners of the wheel because the dressing roller 30 and follower 85 will not be of the same diameter.

As shown in FIG. 2, adjustable earns 40 and 41 are mounted on carriage 11 in position to operate limit switches 13LS and 141.5 respectively.

Switches 12LS and -15LS are mounted on bracket which is attached to housing 61 on slide 12. Oams 51 and 52 for actuating limit switches 12LS and [ISLS are mounted on bracket which, in turn, is attached to carriage 11. Cam 51 includes a spring pressed plunger 53 and cam 52 includes a spring pressed plunger 54. Housing 61 contains the gearing actuated by hand wheel 26 to adjust diamond roller 30 toward and from grinding wheel 15.

The means for movingdresser slide 12 toward andfrom grinding wheel 15 consists of a hold-down cylinder 7%) attached to slide 12 through housing 61 and bracket 50*, and having a piston 71 on piston rod 72 attached to stationary bracket 80. The function of cylinder is -to maintain contact between follower and profile bar 86 to hold follower 85 against profile bar 86. Follower 85 is shown as being'circular in shape, and is also shown as being the same diameter as diamond roller 30. This relation is necessary in order that roller 30 follows the same path with relation to grinding Wheel 15 as follower 85 with relation to profile bar 86. Follower 85 is preferably rotatable, but could be non-rotatable.

Lift cylinder 73 is also attached to housing 61 andhas a piston 74 arranged to contact bracket '80 through piston rod 75.

In the apparatus described above, the dressing tool is a driven roller-type dresser rotatable in a direction transversely of the direction of rotation of grinding wheel '15.

The apparatus shown in FIG. 5 is substantially the same as that shown .in FIG. 4 except that the dressing tool has two spaced single point diamonds. The sliding follower '87 and profile bar 88 are adapted to the diamond-typedresser and are somewhat different from the corresponding elements of FIG. 4. The only other difference between the devices of FIGS. 4 and 5 might be in the longitudinal positions of the cams such 'as 41 and 42, to accommodate them to the spacing of the diamonds. Diamond wear would be more of a factor with the dressing tool of FIG. 5 than with roller 36 of FIG. 4.

In FIG. 10 is shown the extent of traverse movement required to move a roller-type dressing tool to certain points on the corner of a grinding wheel. The traverse movement is always-equal to the radius to be dressed plus the radius-of diamond roller 30. In the diagram, thisis represented by E. The radius shown on grinding wheel 15 might be considered as a minimum radius for crank grinding wheels. As a matter of convenience, roller 30 is shown in contact with a maximum radius for the corner of grinding wheel 15.

In order for roller 30 to dress the first half of the corner, that is, to the 45 point, the straight line traverse movement is represented by A. While roller 30 moves to the second half of the corner, that is, from 45 to 90, the corresponding traverse movement is indicated by B. The traverse movement to place the dressing tool at the 60 point is represented by C, while the traverse movement'forthe last 30 is represented by D.

As indicated above, if a uniform traverse speed is maintained, the second half of the corner will be dressed more rapidly than the first half, or if the 60 point is considered, the last /3 of the dressing operation will be performed at a proportionally faster rate than the first In either case, the quality of the dressed surface of the wheel sufiers as a result of the shorter time permitted for this part of the dressing operation. The quality of the dressing is much improved when the rate of the traverse movement is reduced while the roller 30 operates on this part of the corner. The means for effecting this change in traverse speed will be described later.

Operation Control relay contact ltlQR in the circuit to the dresser start push button is closed when the machine is started and remains closed during the operation of the machine.

To start the dressing operation, the dresser start push button is closed to complete a circuit to energize relay 45CR. A relay contact such as ltlCR closed automatically from a suitable signal might be used instead of a push button.

Control relay contact45CR4 completes a circuit to energize diamond lift valve solenoid 21. Valve solenoid 21 shifts valve 1% to the left directing fluid under pressure to the head end of lift cylinder 73. Piston 74 through piston rod 75 abuts against bracket 80 on carrlage 11 and is thus held against movement.

Cylinder 73 is attached to slide 12 and retracts said slide 12 and roller 30 until cylinder 73 is stopped at point B (FIG. 6) by engagement with piston 74. At this point, roller 30 is in position to engage grinding wheel 15 on the radius at a point some distance below the face of grinding wheel 15. The length of piston rod 75 may be adjusted to change the position of engagement.

Relay contact 45CR2 completes a circuit to energize relay 47CR.

Relay contact 45CR5 completes a circuit to energize relay 46CR.

Relay contact 46CR2 completes a circuit through relay contact 47CR1 to hold relay 47CR.

Relay contact 47CR2 completes a circuit to energize relay SGCR.

Relay contact SQCRZ completes a circuit from limit switch 17LS which is held closed by cam 42 on cam bar 13, to energize relay 57CR.

Relay contact S'EECRS completes a circuit to energize traverse right valve solenoid 19, shifting reversing valve 11% to the right. Valve 110 in the right hand position directs fluid to move traverse piston 121 and roller to the right.

Relay contact 57CR1 completes a circuit to energize dresser fast traverse right valve solenoid 23. Valve solenoid 23 shifts valve 139 to the right connecting exhaust from the right hand end of traverse cylinder 120 with exhaust passage 131 instead of discharging through throttle valve 112 and reversing valve 119. Piston 121 and carriage 11 are driven at high speed. Carriage 11 moves to the right at a rapid rate until cam 42 releases limit switch 1718 at the point where roller 30 engages grinding wheel 15.

Limit switch 17LS opens, deenergizing valve solenoid 23, allowing valve 139 to return to center position, blocking the free escape of exhaust fluid from the right hand end of cylinder 12% so that said fluid must discharge through throttle valve 112, reducing the speed of piston 121, carriage 11 and roller 30 to a rate suitable for dressing the face of grinding wheel 15.

Relay contact 45CR3 closes in the circuit to relay 49CR, but normally open relay contact 48CR1 prevents energizing relay 49CR at this point.

As carriage 11 moves to the right, limit switch contact 14LS1 in the circuit to relay 47CR is opened when released by cam 41, but relay 47CR is held through relay contact 47CR1.

Limit switch contact 14LS2 closes to complete a circuit to energize relay 52CR.

With roller 30 at a suitable point C (FIG. 6) in its 6 path across grinding wheel 15, cam 40 actuates limit switch 13LS, deenergizing relay 45CR.

Relay contact 45CR4 opens to deenergize diamond lift valve solenoid 21 of valve 100 to return said valve to the right. In the right hand posiion, valve 100 directs fluid under pressure to the rod end of lift cylinder 73. The rod end of hold-down cylinder is under a constant pressure substantially lower than that of the fluid supplied to lift cylinder 73. This pressure is determined by relief valve 76. As soon as the fluid to lift cylinder 73 is reversed, fluid in the rod end of lift cylinder 73 acts to move piston 74 to withdraw piston rod 75 from contact with bracket so as not to interfere with the radially inward movement of roller 30 on the corner of grinding wheel 15.

The traverse movement to the right continues until roller 30 reaches point D (FIG. 6) on the radius and below the face of grinding wheel 15. Point D may be anywhere on the first half of the corner.

As indicated previously, if point D is at the 45 point on the corner, the actual traverse movement will be much greater than the extent of the surface of grinding wheel 15 to be dressed. For this reason, it may be desirable to increase the traverse speed momentarily and thus provide a more or less substantial time saving for the complete dressing cycle.

Near the end of the traverse movement to the right, limit switch 17LS is depressed by cam 43 and valve solenoid 24 is energized to provide an unrestricted exhaust of fluid from traverse cylinder 12G, bypassing reversing valve 11% and associated traverse speed throttle valve 1-12. This fast traverse lasts only until limit switch 12LS is actuated by the inward movement of the dressing tool as follower moves around the righthand corner of profile bar 86.

The point of operation of limit switch 12LS by cam 52 may be set for any desired position on the corner. Assunrinig that it is set to operate at the 45 point, the high speed will continue until this point, and while limit switch 17LS will continue to be held by cam- 43, normally closed limit switch 12LS will close due to release by cam 52. Depending on the direction of traverse, one of the relays SGCR or S lCR will remain energized and will complete a circuit from limit switch 12LS through either of the relay contacts of SiBCRl or 51CR1 to energize relay SSCR.

Relay contact SSCR]. will complete a circuit to energize slow traverse valve solenoid 22, shifting valve 140 to the left and connecting the supply of fluid to reversing valve 116 with throttle valve 142. Even though the fast traverse valve is actuated by limit switch 17LS to provide an unrestricted exhaust, the rate of traverse at this point is determined by the setting of throttle valve 142 in the pressure supply from the pump.

The slight inward movement of roller 30 at this point releases limit switch 12LS and completes a circuit to energize traverse slow down valve solenoid 22, shifting slow down valve 14010 the left, blocking the unrestricted fluid supply through valve and connecting line 141 with a restricted supply through throttle valve 142. Line 141 conducts fluid to reversing valve 11!) which is in its left hand position.

The reduced flow of fluid results in a slow down of traverse piston 121 and roller 30 until point E (FIG. 6) is reached at a rate to prevent uncontrolled movement of roller 39 by hold-down cylinder 70 as it moves around the final portion of the corner of grinding wheel 1'5. As a result of this reduction in traverse speed, roller 30 will dress this portion of the wheel corner so that it will produce the best possible finish on the corresponding portion of the workpiece.

At this point, limit switch contact 15LS1 is released and the circuit through relay contact 46CR1 is opened, deenergizing relay 46CR. Relay contact 46CR2 opens the circuit through relay contact 47CR1, deenergizing valve solenoid 19 and permitting reversing valve 110 to return to centralposition. In this position, the movement ofroller 39 to the right is stopped.

Relay contact SGCRl opens the circuit to relay SSCR and relay contact 'SSCRl opens to deenergize traverse slow down valvesolenoid 22..

Slow down valve 140 is returned to the right to connect reversing valve 118 to the unrestricted pressure supply.

At the end of the traverse movement to the right, limit switch contact 14LS1 is opened and limit switch contact 14LS2 is closed.

Limit switch contact 14LS2 completes a circuit to energize relay SZCR.

Relay contact 52CR1 completes a circuit from limit switch con-tact '15LS2 to energize relay 48CR.

Relay contact 48CR1 completes a circuit to energize relay 45CR.

Relay contact 45CR4 closes to complete a circuit to energize lift valve solenoid 21. Valve solenoid 21 shifts valve 100 to the left directing fluid to the head end of lift cylinder 73 to withdraw roller 30 from point E to point F (FIG. 6).

Relay contact 45CR3 completes a circuit through relay contact 425C112 to energize relay 49CR.

Relay 490R is held through relay contact 49CR1.

Relay contact 49CR2 completes a circuit to energize relay 51CR.

Relay Contact SICRS completes a circuit to energize traverse left valve solenoid 20 which shifts reversing valve 110 to the right to'direct fluid under pressure to the rod end of traverse cylinder 120, shifting piston 121, carriage 1:1 and roller 30 to the left. At the same time, relay contact 51CR2 completes a circuit from limit switch 1718 which is held closed in either end position of carriage 11 by cams 42 and 43 to energize relay 58CR.

Relay contact 58CR1 completes a circuit to energize fast traverse left valve solenoid 24, shifting valve 130 to the left and connecting the left end of cylinder 12% directly to the unrestricted exhaust passage 131 instead of passing through throttle valve 111 and reversing valve 116 to the same exhaust line.

The traverse movement to the left thus begins at a fast rate and continues at this rate until point D is reached in FIG. 6. At this point, limit switch 1'7LS is released by cam member 43 and opens the circuit through relay contact 51CR2 to deenergize relay 58GB.

Relay contact SSCRI opens to deenergize fast traverse left valve solenoid 24.

Fast traverse valve 134 is returned to its central posi tion cutting off the free exhaust of fluid from the left end of cylinder 120 so that such exhaust fluid must pass through throttle valve .1 11 and the left end of reversing valve 110 to exhaust passage 131.

Throttle valves 115 and 116 in the fluid lines connected to opposite ends of cylinder 120 are bleeder valves which are used to remove the accumulation of air from cylinder 120 usually after the machine has been idle for some time.

The traverse movement of roller 30 to the left continues at a rate suitable for dressing.

At point C (FIG. 6), limit switch 13LS is released by cam 40 opening a circuitthroutgh relay contact QSCRI to deenergize relay 45CR.

Relay contact 45CR4 opens, deenergizing lift valve solenoid 211, permitting valve 100 to return to the right and direct fluid under pressure to the rod end of lift cylinder 73.

Lift piston 74 is moved to withdraw piston rod 7'5 from engagement with bracket 80 so that hold-down cylinder 70 may urge follower 85 against roller 36 without interference from piston rod 75.

The traverse left movement continues until roller 36 8 reaches point G (FIG. 6) on grinding wheel 15. At this point, which is on the curved portion of the wheel corner, roller 39 has moved inwardly under the influence of holddown cylinder 79, follower and profile bar 86.

Limit switch IZLS is released to complete a circuit through control relay contact .51CR1 to energize relay SSCR.

Relay contact 55CR1 completes a circuit to energize traverse slow down valve solenoid 22 to shift slow down valve 140 to the left. This requires the supply of fluid to reversing valve 116 and transverse cylinder 120 to pass through throttle valve 142, thus reducing the traverse rate as roller 30 moves inwardly on the radius of grinding wheel corner toward point A (FIG. 6). Holddown cylinder 70* joins with motor 31 in effecting this movement.

At point A (FIG. 6), limit switch 15LS is released, opening limit switch contact 15LS1 and closing limit switch contact 115LS2.

Limit switch contact 15LS1 opens the circuit through relay contact 46CR1 to deenergize relay MGR.

Relay contact 46CR3 opens a circuit through relay contact 49CR1 to deenergize relay 49CR.

Relay contact 49CR2 opens a circuit to deenergize relay SICR.

Relay contact '51CR3 opens a circuit to deenergize traverse left valve solenoid 20.

Reversing valve 110' is returned to central position, stopping the traverse movement and ending the dressing operation.

Relay contact 51CR1 opens to deenergize relay SSCR.

Relay contact 55CR1 opens to 'deenergize slow traverse valve solenoid 22.

Slow down valve is returned to the right hand position to provide for a normal dressing traverse rate for the next grinding cycle.

At point A (FIG. 6), limit switch contact 14LS1 is actuated by cam 41to set up a circuit through relay contact 45CR2 to energize relay 47CR at the beginning of the next dressing cycle.

In FIG. 11 is shown a slightly modified hydraulic circuit in which the same control elements shown in FIG. 9 are used with little or no change in electrical connections.

Selector valve is situated in the exhaust line from reversing valve 110. The exhaust line from valve 110 is divided at a point close to valve 150 connected to said valve at three spaced points. These being identified by S, N, and F, representing the traverse speeds slow, normal, and fast respectively. Valve 150 consists of two wide land portions separated by a relatively narrow open portion so that only one of three exhaust connections will be open at one time.

On the opposite side of valve 150 are three exhaust conduits corresponding to the connections mentioned above and arranged to provide passage through valve 150 from one connection or the other. On the opposite side of valve 150, there is a throttle valve on each line, one set for fast speed and indicated at F, another set for normal speed and indicated at N, and the third set for slow speed and indicated at S. The outlet ends of these throttle valves are all joined together in a single exhaust conduit.

During normal traverse of roller 30', valve 150 is held in center position by two springs. In this position, exhaust fluid is directed through throttle valve N so that traverse piston 121 will travel at'a speed suitable for dressing the face of grinding wheel 15. a

At the beginning of the traverse movement, limit switch 17LS will function through either relays 570R or SSCR to energize valve solenoid 24 to shift valve 150 to the left. In this position, exhaust fluid will be directed through throttle valve F which permits a maximum rate of flow of exhaust fluid so that roller 30 may be moved rapidly into wheel engaging position.

Toward the end of the traverse movement of roller 30 across the work, as it begins to move inwardly under the control of profile bar 86 and follower 85, cam 52 releases limit switch 12LS which closes a circuit through either relays SQCR or SlCR to energize relay SSCR.

Relay contact 55CR1 energizes valve solenoid 22. Normally closed relay contact 5CR2 opens to deenergize valve solenoid 23.

Valve solenoid 22 shifts valve 159 to the right and directs exhaust fluid through slow speed traverse valve S to reduce the traverse rate during the dressing of the second half of the corner of grinding wheel 15.

By controlling the speed of the traverse movements through a selector valve as described above, fast speed valve 13% and slow speed valve 140 may be omitted.

We claim:

1. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a dresser bar for supporting said dressing tool, said dressing tool comprising a diamond roller rotatable about an axis in a plane tilted from the horizontal and in a direction normal to that of said grinding wheel, means for rotating said diamond roller, a carriage for supporting said dresser bar and movable longitudinally to move said dressing tool across said grinding wheel, hydraulic motors for effecting each of said movements, guide means for said dressing tool comprising a profile bar and follower, means to maintain a constant pressure on one side of the transverse moving or hold-down hydraulic motor to maintain contact between said follower and said profile bar, a third motor operable in opposition to said hold-down hydraulic motor to lift said dressing tool free of said grinding wheel to a point on the radius below the face of said grinding wheel, control means operable at the beginning of a dressing operation to actuate said hold-down hydraulic motor and said lift motor simulaneously, control means for retracting said lift motor at a predetermined point in said transverse movement so as not to interfere with said hold-down hydraulic motor as said dressing tool moves inwardly on said rounded corner, control means operable toward the end of said traverse movement for reducing the rate of said traverse movement as said dressing tool follows said profile bar to dress a radius on the corner of said grinding wheel, control means operable at the end of said traverse movement to reverse said traverse movement and to actuate said lift motor to retract said dressing tool to a point below the face of said grinding wheel, said traverse movement being repeated in the opposite direction, and control means operable at the end of said second traverse movement to stop said dressing operation.

2. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to move said dressing tool across said grinding wheel, hydraulic motors for effecting each of said movements, guide means for guiding said dressing tool to dress the face and corners of said grinding wheel, means for traversing said dressing tool under the control of said guide means to engage said grinding wheel at a point on the radius below the face of said grinding wheel determined by said guide means, and control means operable when said dressing tool reaches the other side of said grinding wheel to change the speed of said traverse movement while said dressing tool is guided around said corner, and means on said carriage for actuating said control means.

3. Means for dressing a grinding wheel having rounded corners comprising a power driven dressing roller rotatable about an axis normal to the grinding wheel axis and in a plane other than that passing through said grinding wheel axis, said dressing roller being movable transversely toward and from said grinding wheel, a carriage for supporting said dressing roller and movable longitudinally to move said dressing roller across said grinding wheel, power means for effecting each of said movements, guide means for guiding said dressing roller around the corners of said grinding wheel, and means for changing the speed of said longitudinal movement while said dressing roller is guided around said corners.

4. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to move said dressing tool across said grinding wheel, hydraulic motors for effecting each of said movements, guide means for guiding said dressing tool to dress the face and corners of said grinding wheel, means for retracting said dressing tool before each pass of the dressing tool across said grinding wheel to a point on the radius below the face of said grinding wheel determined by said guide means, control means to start said traverse movement at a relatively rapid rate to traverse said dressing tool into operative relation with said grinding wheel, control means operable as a result of the rapid traverse movement to reduce said traverse speed to a dressing speed, and control means operable at the other end of said traverse movement as said dressing tool moves inwardly to dress the wheel corner, to reduce said traverse speed to a rate below the normal dressing rate until the end of said traverse movement.

5. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to pass said dressing tool across said grinding wheel, a hydraulic motor for effecting said longitudinal movement, a profile bar and follower for guiding said dressing tool to dress the face and corners of said grinding wheel, means for holding said profile bar and follower in contact with one another, a second hydraulic motor for opposing said contact maintaining means, means for actuating said second hydraulic motor at the beginning of each pass of said dressing tool to move said dressing tool transversely of the direction of said longitudinal movement to a position on the corner below the face of said grinding wheel, means actuated by said outward movement of said dressing tool to actuate said first mentioned hydraulic motor to move said dressing tool longitudinally, means operable in response to said longitudinal moving means to reverse said second hydraulic motor to restore contact between said profile bar and follower, said contact maintaining means serving to assist said longitudinal moving means to move said dressing tool in an arcuate path around the corners of said grinding wheel.

6. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to traverse said dressing tool across said grinding wheel, hydraulic motors for effecting each of said movements, guide means for guiding said dressing tool to dress the face and corners of said grinding wheel, means for retracting said dressing tool before each pass of the dressing tool across said grinding wheel to a point on the corner below the face of said grinding wheel, control means to start said traverse movement at a relatively rapid rate to traverse said dressing tool into operative relation with said grinding wheel, and then to reduce said traverse speed to a dressing speed, means operable at theother end of said traverse movement to actuate said control means to repeat said rapid movement as said dressing tool passes over the first portion of the wheel corner, and another control means operable thereafter to change the traverse speed of the dressing tool on the second portion of said wheel corner to a speed less than said normal dressing speed.

7. Means for dressing a grinding wheel having rounded corners comprising a power driven dressing roller rotatable about an axis normal to the grinding wheel axis and movable transversely toward and from said grinding wheel, a carriage for supporting said dressing roller and movable longitudinally to move said dressing roller across said grinding wheel, hydraulic motors for effecting each of said movements, guide means for guiding said dressing roller to dress the face and corners of said grinding wheel, means to dress the face and one corner of said grinding wheel in one direction of traverse, means to dress the face and the other corner of said grinding wheel in the other direction of traverse, and means to change the speed of said traverse movement while dressing said corners.

8. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to move said dressing tool across said grinding wheel, hydraulic motors for effecting each of said movements, guide means for guiding said dressing tool to dress the face and corners of said grinding wheel, control means operable at predetermined points in the path of the dressing tool to control the speed of said longitudinal movement whereby to provide one speed for dressing the face of said grinding wheel, another speed for dressing the portions of the corners adjacent the face of said grinding wheel, and a third speed for dressing the portions of said corners adjacent the sides of said grinding wheel, and means on said carriage independent of said guiding means for actuating said control means.

9. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to move said dressing tool across said grinding wheel, hydraulic motors for elfecting each of said movements, guide means for guiding said dressing tool to dress the face and corners of said grinding wheel, and means to control the speed of said longitudinal movement including a selector device having a plurality of restrictions, and means operable by said carriage at predetermined points in said longitudinal movement for actuating said selector device to provide the longitudinal speed suitable for that portion of the dressing operation.

10. Dressing means for a grinding wheel comprising a power driven dressing roller rotatable in a plane normal to the plane of said grinding wheel with the face of said dressing roller inclined away from the face of said grinding wheel, means for moving said dressing roller toward and from said grinding wheel along a path passing through the axis of said grinding wheel, a carriage for supporting said dressing roller, and means for moving said carriage longitudinally to move said dressing roller across said grinding wheel.

11. Means for dressing a grinding wheel having rounded corners comprising a power driven dressing roller rotatable about an axis normal to the grinding wheel axis and with the peripheral face of said dressing roller inclined away from the face of said grinding wheel, means for moving said dressing roller transversely toward and from said grinding wheel, a carriage for supporting said dressing roller and means to move said carriage longitudinally to move said dressing roller across said grinding wheel, power means for effecting each of said movements, guide means for guiding said dressing rollertaround the corners of said grinding wheel including a forming bar and a roller follower, part of said dressing roller having the same diameter as said follower, and means for reducing the rate of said longitudinal moving means so as to control the rate of said transverse moving means as said dressing roller is guided around said corners.

12. Means for dressing a grinding wheel having rounded corners comprising a power driven dressing roller rotatable about an axis normal to the grinding wheel axis and in a plane other than one passing through said grinding wheel axis, means for moving said dressing roller transversely toward and from said grinding wheel, a carriage for supporting said dressing roller and means for moving said carriage longitudinally to move said dressing roller across said grinding wheel, and power means for effecting each of said movements, guide means for guiding said dressing roller around the corner of said grinding wheel, and control means operable when said dressing roller reaches a predetermined point on the corner of the wheel for reducing the rate of said longi tudinal moving means while said dressing roller is guided around said corner.

13. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to move said dressing tool across said grinding Wheel, hydraulic motors for effecting each of said movements, guide means for guiding said dressing tool to dress the face and corners of said grinding wheel, and limit switch means actuated by one or the other of said movable members to control said longitudinal and transverse movements whereby to provide a slow feed for dressing the face of said grinding wheel, a fast feed for dressing the portion of said corner adjacent the face of said grinding wheel and a feed slower than said first mentioned slow feed for dressing the portion of the corner adjacent the sides of said grinding wheel.

14. Means for dressing a grinding wheel having rounded corners comprising a dressing tool movable transversely toward and from said grinding wheel, a carriage for supporting said dressing tool and movable longitudinally to move said dressing tool across said grinding wheel, hydraulic motors for effecting each of said movements, guide means for guiding said dressing tool to dress the face and corners of said grinding wheel, control means responsive to said longitudinal movement to provide a slow feed for dressing the face of said grinding wheel and a fast feed for dressing the portion of said corner adjacent the face of said grinding wheel, and other control means responsive to said transverse movement to provide a slower feed than said longitudinal movement for dressing the portion of the corner adjacent the sides of said grinding wheel.

15. Means for dressing a grinding wheel comprising a dressing roller mounted for rotation in a plane normal to the plane of the grinding wheel with its peripheral face inclined so that initial engagement of the dressing roller with the peripheral face of the grinding wheel is on one edge of the dressing rolier, means for moving said dressing roller toward and from said grinding wheel along a path passing through the axis of said grinding wheel, a carriage for supporting said dressing roller, and means for moving said carriage longitudinally to move said dressing roller across said grinding wheel.

16. Means for dressing a grinding wheel having rounded corners comprising a power driven dressing roller rotatable about an axis normal to the grinding wheel axis and in a plane parallel to said grinding wheel axis, said dressing roller being movable toward and from said grinding wheel radially thereto, a carriage for supporting said dressing roller and movable to traverse said dressing roller across the periphery of said grinding wheel, power means for effecting each of said movements, guide means for guidin said dressing roller around the corners of said grinding wheel, and means for changing the speed of said traverse movement of said dressing roller while it is being guided around said corners.

17. A dressing device for grinding wheels having rounded corners comprising a power driven dressing roller movable toward and from said grinding wheel, a carriage for supporting said dressing roller and movable to move said dressing roller across the periphery of said grinding wheel, means for guiding said dressing roller around the corners of said grinding wheel comprising a forming bar on said carriage and corresponding to the shape of said Wheel, a follower movable with said dressing roller and having a diameter the same as the diameter of said dressing roller, means for maintaining the diameter of a portion of the operative face of said dressing roller equal to the diameter of said follower comprising means for supporting said dressing roller in a plane normal to the plane of said grinding wheel with the peripheral face of said dressing roller inclined away from the peripheral face of said grinding wheel.

18. Means for dressing a grinding Wheel comprising a power driven dressing roller, means for rotatably supporting said dressing roller in a plane normal to the plane of said grinding wheel with the peripheral face of said dressing roller inclined away from the peripheral face of said grinding wheel so that initial contact between 14 said dressing roller and said grinding wheel is on one edge of said dressing roller, a carriage for supporting said dressing roller, and means for moving said carriage parallel to the axis of said grinding wheel to cause said dressing roller to move across the operative peripheral face of said grinding Wheel.

References Cited in the file of this patent UNITED STATES PATENTS 2,449,372 Englinton et a1. Sept. 14, 1948 2,602,437 Tancred July 8, 1952 2,659,359 Hill Nov. 17, 1953 2,697,426 Price Dec. 21, 1954 2,861,561 Olson Nov. 25, 1958 2,907,315 Hill Oct. 6, 1959 2,963,017 Narel Dec. 6, 1960 

18. MEANS FOR DRESSING A GRINDING WHEEL COMPRISING A POWER DRIVEN DRESSING ROLLER, MEANS FOR ROTATABLY SUPPORTING SAID DRESSING ROLLER IN A PLANE NORMAL TO THE PLANE OF SAID GRINDING WHEEL WITH THE PERIPHERAL FACE OF SAID DRESSING ROLLER INCLINED AWAY FROM THE PERIPHERAL FACE OF SAID GRINDING WHEEL SO THAT INITIAL CONTACT BETWEEN SAID DRESSING ROLLER AND SAID GRINDING WHEEL IS ON ONE EDGE OF SAID DRESSING ROLLER, A CARRIAGE FOR SUPPORTING SAID DRESSING ROLLER, AND MEANS FOR MOVING SAID CARRIAGE PARALLEL TO THE AXIS OF SAID GRINDING WHEEL TO CAUSE SAID DRESSING ROLLER TO MOVE ACROSS THE OPERATIVE PERIPHERAL FACE OF SAID GRINDING WHEEL. 